thomson



(No Model v 2 Sheets-Sheet 1. E. THOMSON.

ELECTRIC LAMP.

No. 253,958. Patented Feb. 21,1882.

(No Model.) 2 Sheets-Sheet 2. E. THOMSON;

ELECTRIC LAMP.

No. 253,958. Patented Feb. 21,1882.

UNITED STATES PATENT OFFICE.

ELIHU THOMSON, OF NEW BRITAIN, CONNECTICUT, ASSIGNOR TO THE AMERICAN ELECTRIC COMPANY, OF SAME PLACE.

ELECTRIC LAMP.

SPECIFICATION forming part of Letters Patent No. 253,958, dated February 21, 18 82.

Application filed April 9, 1881. (No model.)

To all whom it may concern:

Be it known that I, ELIHU THOMSON, of New Britain,county of Hartford, State of Connecticut, have invented certain new and useful Improvements in Electric Lamps of the arc type, of which the following is a specification.

The object of my invention is to provide a simple, effective, and compact regulator for electric lamps, by means of which an electric arc is maintained between two carbons, and a delicate and almost imperceptible feeding of the carbons as fast as they are consumed secured without the use of dash-pots, wheel-work, or

the like.

Figure l is a side view of the regulating mechanism of a lamp constructed in accordance with my invention. Fig. 2 is an end view, cutting Fig. 1 through dotted line a; a". Figs. 3 and 4. show the form of the magnetpoles used. Fig. 5 is a detailed view of the peculiar clamp used in my invention and its relation to the other parts of the lamp. Figs. 6 and 7 are modified forms of clamp, Fig. 5. Figs. 8 and 9 show the mode of hanging the lamp, so that it may he raised and lowered and simultaneously removed from the circuit or placed in the circuit without breaking the continuity of said circuit. Fig. 10 shows an attachment which I prefer to place in a lamp for the purpose of allowing the carbon-holding rod easily to be kept clean and bright.

In Fig. 1, R is a rod supporting the upper carbon pencil, upon which rod is placed a clamp, O. The body O of the clamp is upheld by supports from abentlever, L, pivoted at I, as shown,

and any change in the position of the lever L is imparted to the body of the clamp 0. At each of the extremities of the bent lever 11 are placed masses of iron perforated with openings rounded out, as shown in Figs. 3 and 4, for encircling the prolongation of the magnet-poles B and D, which have a peculiar tapered form. The magnet M is traversed by the direct current, while K is traversed by a derived current around the are. A spring, S, serves to counterbalance, if need be, any undue excess of power in the magnet M. By placing the core of the magnet M in magnetic connection with the in closing-box, which is of iron, and causing the iron end of the lever L to move near the side v of the inclosing-box, a very much increased attraction of the magnet M for its armature is obtained by reason of the magnetic circuit of M being nearly completed through it and the box-sides. I prefer to use one magnet M, constituting a barmagnet, and two coils, K K, Fig. 2, the latter connected to constitute a single electro-magnet ofordinary form, except that the polar projectionsD are prolonged, as shown. The form of the prolongations B and D, and the opening in the armatures into which they project at the ends of the lever L, is such that with a uniform current strength a practically uniform attractive force is obtained through a considerable range of position of the armature. Figs. 8 and 4 are enlarged views of the relations by which I obtain the result just mentioned. The pole B of the magnet M, Fig. 3, is of a conoidal (preferably paraboloidal) or of a tapered form, while the opening in the armature encircles it and has preferably rounded edges, as shown. By this combination the increasing force due to the approach of the armature and its greater proximity to the sides of the pole is balanced by the outward attraction of that part of the pole B projecting through. the armature, and the result is a pull or attraction uniform in various positions. I am not aware that this result of uniformity in various positions has ever before been attained in an electro-magnet with fixed pole and movable armature. It is to be attributed to the balance established between the polar attractive force outward from the magnet and that toward the magnet due to the form and disposition of the magnet and the projection of the pole through or beyond the armature in most positions.

I am aware that magnets with hollow poles and conical armatures entering therein, as also magnets having poles of uniform cross-section and perforated armatures, have been known and used but they fail to give the result desired, as there is no balance existing between outwardly and inwardly acting attractions, the sole efi'ect being an attraction toward the body of the magnet, while in my invention, with an armature as described and shown, that part of the pole of the magnet projecting beyond the armature exerts an attraction away from said magnet,and thus counterbalances any tendency to increased force when the armature is very near the pole. When the ordinary flat pole and flat armatures are employed the changed attractive energy in various positions requires to be balanced by the action of opposingsprings-amatter of considerabledifficulty.

The form of electromagnet and armature above described is applicable to other uses besides for electric lamps, and may be employed in any position where a considerable range of motion may be desired in a field where a uniform current strength will produce a practically uniform attractive force. I do not therefore desire to'limit myself to the particular. application of such an eleetro-magnet as is herein described.

Fig. 5 shows the construction of the clamp C, Fig. 1, in detail and its relation to the neighboring parts. The body 0 supports two jaws, T and T, one fixed the other pivoted, which are adapted to bear against the rod R on opposite sides thereof. The jaw T, pivoted at c, has an extended arm, t, provided with a retractil'e spring, Z, one end of which is attached to the frame or astationary part of the lamp. Ifthe clamp O isin such position that the spring Z can hold the extremity it down, the toesurfacef is held firmly against the rod It, sustaining it and preventing its vertical descent; but if the clamp 0 be lowered by the fall of the lever L, the prolongation t finally rests on the stationary stop P, and the toe T, being relieved of the force of the spring Z, permits the descent of the rod past the clamp O. The peculiar feature of this clamping device which distinguishes it from all others and results in a slow downward motion of the rod B through it instead of ajerky or sudden fall, is the extreme delicacy with which the pressure and friction of the clutch against the side of the rod R are adjusted. This is obtained by the leverage afforded by the prolongation t, bothfor the action of the spring Z in holding the toe in place and the pressureonP in releasing it. The angle of impingement of the toeT against the rod It is such that without the assistance of the spring Z, or cquivalen t,it would be inoperative to hold the rod B, so that its action at all times is that simply of a friction-clutch, the amount ofwhose friction depends only upon the amount of force exerted by the spring Z, and is not affected by the weight of the carbon-holder. It is not therefore a self-locking clutch, such as are commonly employed in drop and lift electric lamps, and the result of its operation is not to cause a feeding of the carbons by dropping them into contact and afterward lifting them quickly apart, but the extreme delicacy of action is such that I am able to obtain a feeding motion so slow and gradual as to render it difficult to detect without actual measurement.

Figs. 6 and 7 show modified forms of clamp acting as that shown in Fig. 5, and similar letters of reference designate similar parts. In Fig. 6 the jaws bear upon the rod at a point below the line joining their points of support.

In other respects the arrangement is the same as in Fig. 5. In Fig. 7 the jaw T is supported in an upright position on the armature-lever. The jaw T encircles the rod and is pivoted to T. Itisprovided with a friction-toe, as shown, upon the opposite side of the rod from T.

The operation of the devices is as follows: When the lamp is started the carbons are in contact, and the end N of the leverL is down. The toe T resting on the pillar 1? does not press against the rod, and the rod R is free. When the current circulates through M its raises the armature N of the lever, elevating the clamp G and bringing the toe T and spring Z into action, so as to seize the rod and lift it, thus establishing an arc. The clamp continues to lift the carbon-holder until the are formed between the electrodes is long enough to cause a portion of the current to branch through the shunt-magnet K, thus rendering it active in attracting the upper armature of the lever L. This action continues until the magnet K, assisted by the spring S, balances in its attraction that of the magnet M. By consumption of the electrodes the are lengthens, its resistance increases, and the magnet K becomes stronger, overcoming the force of M at the other extremity of the lever and lowering the clamp O and its extension until the friction of the toe T is sufficiently diminished to allow a slow slipping of the rod It downward. From this period a slow slip takes place as fast as the carbons are consumed, by virtue of the delicate action of the clamp -body 0, its toe T, and spring Z.

It may sometimes happen from some accidental cause that the feeding of the carbon-rod fails to take place, although the clamp is fully released, and a long flaming are is the consequence, which, it continued, when a number of lamps are run in series, may result in an open circuit and general extinguishment. It is customary to provide an automatic cut-out mechanism to shunt the lamp when its are has an abnormal resistance; but I prefer to employ mechanism for forcing the approach of the carhon-electrodes before cutting out the lamp.

I have described in another application for Letters Patent a safety-magnet attachment serving this purpose, and do not therefore herein make claim to it. In the present case I use a special construction of said safety-magnet, having some advantages in working and ease of construction. I place in the lamp-box a small bar electro-magnet, V, Fig. 1, supported at one end and having an armature, W, pivoted at g, the pivots moving in horizontal slots in the support, to allow a to-and-fro horizontal play of the armature NV. The armature bears on its other end, and on the opposite side of the rod R to the magnet V, a piece of rubber or leather, j. A spring, 0, holds the armature W-completely free of the rod R and in an elevated position, as shown. When the magnet V is unexcited or without current a pair of spring-contacts, 11 g, closed one upon the other, maintain a closed circuit around V and keep it inactive. If, however, the power of the shunt-magnet K becomes excessive from abnormal arc-resistance, the contacts 12 q are opened by consequent movement of the lever L, which is provided with a lug or projection, as shown, arranged to impinge against the upper side of the spring q, and the current flowing through V causes it to become active, attracting the armature W, which is carried toward the magnet downward and horizontally, on account of the pivot-slots at g, thus bringing the piecej violently into contact with the rod B by a downward thrust of suificient force to free the parts and cause the approach of the carbons and the restoration of the are.

The general circuits in the lamp, which are indicated in Fig. 1, are as follows: Entering at the point 1 the current divides, the larger portion passing through the points 1) q to the electro-magnet M, to the upper carbon-holder, to the arc, and through a wire, 5, suitably connected with the supports of the lower carbon, to the point 2. The derived circuit in which electro-magnet K is placed is indicated by the Fig. 6.

The renewal of the carbons in a lamp is generally efiected by closing a switch around the lamp before placing in the'new carbons. It is, however, often very inconvenient to so operate when the lamp is hung at a considerable height, as it is then necessary either to renew the carbons with the lamp in place or to lower it to a convenient height before so doing. In the latter case a considerable length of flexibleconductormustexisttomaintainthelampin circuit during raising and lowering. I obviate this inconvenience by the employment of devices arranged so that the raising of the lamp into its place puts it into circuit without breaking the main circuit. This I efi'ect by the arrangement shown in Figs. 8 and 9.

Conveniently placed at the position where the lamp is hung when in use are two short plate-sprin gs, constituting the connections to the positive and negative circuit -wires, so placed as to spring firmly together, as shown in Fig. 6, A. Each lamp is provided with two plates of metal with insulation, between which are respectively the positive and negative con nections to the lamp.

Lamp X, Fig. 8, (shown as lowered by suitably-arranged pulleys and cords, as usual in the art,) bears the two plates a I), one connected electrically to the upper carbon, the other to the lower carbon. By raising the lamp into the position shown in Fig. 9 the contact-pieces a b are inserted between the opposing surfaces of the springs at A and the lamp isintroduced into the circuit. Upon the removal of the lamp the springs A come together, completing the circuit.

In many situations it is necessary to keep the rods R of an electric lamp in good condition by frequent rubbing with very fine emery or crocus cloth. This I elfect by a simple attachment to the lamp itself, which is brought into use by the attendant when renewing the carbons. Fig. 10 shows the device. An are, 0, lined with crocus cloth or felt impregnated with rouge is placed near the carbon-rod It, and furnished with a spring, F, or the like, holding it away from said rod, as shown. By pressing the end h inward toward the rod R the crocus surface is thrown against the rod and the rod now moved up and down accompanied by a rotation given by the attendant, so as to bring nearly the whole surface in contact with the cleansing-surface 0.

By placing the are c in position as part of the lamp mechanism in the regulator-case pressure may be easily brought upon it during the cleansing operation, and it springs away from the rod when relieved.

I am aware that the electro-magnets in the derived circuit and direct circuit acting to control the position of carbon-electrodes are well known in the art, my invention consisting in the peculiar combination of parts, as described, for effecting a gradual feedin gof the electrodes and maintaining an are between the electrodes of nearly constant length with a constant current, and in devices for efi'ecting a sure approach of the electrodes together when an abnormal arc length is by accident attained.

I claim- 1. The combination, substantially as described, with the regulating mechanism of an electric lamp, of an electro-magnet provided with a polar projection, conoidal or tapered in form, and an armature less in thickness than the extent of the tapered portion of said projection, substantially as and for the purpose set forth.

2. The combination, substantially as described, with the regulating mechanism of an electric lamp, of an electro magnet provided with a conoidal or tapered projection, and a perforated armature encircling said projection and less in thickness than the extent of the tapered portion thereof, so that it may move in a field of force, where its motion results from the difference of attraction toward the body of the core, and toward the polar projection extending beyond said armature, as and for the purpose set forth.

3. The combination, with the regulating mechanism of an electric lamp, of an electromagnet having a paraboloidal pole, and aperforated armature encircling said pole, and adapted to move between the extremity of the polar projection and the body of the core, substantially as and for the purpose set forth.

4. The combination, with the regulating mechanism of an electric lamp, of an electromagnet having a tapered pole, and an armature provided with an opening whose inner edges are rounded, as shown and described.

5. In an electric-light regulator, asafetydevice consisting of an electro-magnet, V, arma ture W, pivoted in a slot, impact surface j, adapted to engage with the carboncarrier, and spring 0, substantially as described.

6. In an electric-light regulator, a safety de vice consisting of an electro-magnet and a pivoted and sliding armature carrying an engaging-piece to strike and impel the carbon-carrier, substantially as described.

7. The combination, with an electric lamp, of two divided insulated plates, constituting the poles of the regulator and attached to the frame of the lamp, two circuit-closing springs, as described, in permanent connection with the general circuit, and fixed to the frame or support from which the lamp is hung, and means for lowering and raising the lamp into position, all combined as described, so that when the lamp is raised the springs are separated 

